In recent years, there is increased a case where a portable information communication terminal, such as a cellular phone, a smartphone, or a PDA (personal digital assistant), downloads and installs an application via radio waves or via a personal computer (PC). For example, there is a Java® application in a cellular phone. A user is able to execute a Java® application of his/her choice on a cellular phone by selecting the Java® application out of a browser or the like and downloading the application into the cellular phone.
It is expected that portable information terminals, having functions added by downloading applications in this manner, continue to increase in the future.
There are three timings for downloading an application as follows:    1. At user selection    2. At trigger detection    3. On-demand
The timing “1. At user selection” is applied to a method of performing the download when a user selects the information (performing the download) from a browser or the like by a user operation. The timing “2. At trigger detection” is applied to a method of performing the download when a certain condition, such as time and place, is satisfied. The timing “3. On-demand” is applied to a method of performing the download by an application calling another application. In the present invention, the action, in which an application calls and causes another application to perform some processing, is referred to as “application interaction.” If the call target application is not found in the terminal, the application is downloaded from a server on a network in some cases.
The present invention targets at the above “3. On-demand.” The problems of the on-demand method include that the processing appears to stop to the user because of long download time and that, in the case of an unavailable network, the user cannot perform the download and thus cannot continue the processing. This requires a method of estimating required applications in advance to complete the download of the applications before calling.
In addition, the portable information communication terminal is limited in resource in comparison with the PC, and thus downloading all of the related applications compresses the storage space. Further, an increase in the number of applications to be downloaded or in the downloading size increases the content fee, packet fee, or other fees correspondingly. Therefore, it is necessary to download applications thought to be really required.
As documents describing a technique of extracting required or related applications, there are, for example, Patent Document 1 and Patent Document 2. The Patent Document 1 describes a method of displaying a list of frequently-called methods in a position, to which a user easily access, in making a list of method call relationships.
Moreover, Patent Document 2 describes a method of previously acquiring (prefetching) appropriate completed works (files, applications, or the like) into an appropriate application server at a thin client terminal.